Galactic O-star catalog


Query the catalog and supplements



This Galactic O-Star Catalog (GOSC) is the third version of an ambitious project to include as much accurate information related to this type of objects as possible. This version includes cross-references to other catalogs, spectral classifications, astrometric information, basic photometry, and cluster/association membership.

GOSC places a special emphasis on the uniformity of the spectral classification used. In order to satisfy that requirement, the first version of the catalog was built in 2002 starting with the 350 Galactic O stars catalogued by Nolan R. Walborn over the years and adding a few stars with reliable spectral classifications. With the second version of the catalog we added 800 stars from the literature in 2006 but we soon discovered that many of those spectral types were unreliable. As a consequence, we started the Galactic O-Star Spectroscopic Survey (GOSSS) with the intention of obtaining modern blue-violet spectra with R = 2500 of all Galactic stars that had at least one previous classification as O or B0. In June 2013 GOSSS became the basis for the spectral types in the third version of GOSC. The current version lists the 611 O stars, 32 BA stars, and 12 late-type stars in GOSSS-DR2.2. Future versions will include additional Galactic O stars as well as other stars in supplements.

If you use the Galactic O-Star Catalog, please refer to it as:
Maíz Apellániz, J. et al. (2013), in Massive Stars from α to Ω.

If you use the Galactic O-Star Spectroscopic Survey, please refer to it as:
Maíz Apellániz, J. et al. (2011), Highlights of Spanish Astrophysics VI, p. 467.


(1) Basic identifications (mandatory)

name:     Most common name.
#: Query running number.

Flag that indicates whether the star belongs to the main catalog (Ma) or to a supplement (S1,S2...).

dc: (For cone searches only) Distance to center.
PA(o): (For cone searches only) Position angle with respect to center (N=0, E=90).

Galactic O Star (GOS) catalog number, created according to IAU nomenclature rules (note that v0.x of the catalog used a different designation). The first character is a G, the next six express the Galactic longitude in degrees in the format LLL.ll, the eighth character is the latitude sign, the next five express the absolute value of the Galactic latitude in degrees in the format, the fourteenth is an underscore, and the fifteenth and sixteenth are a running number to differentiate stars which would otherwise have the same catalog number.


Link to GOSSS spectrum in FITS format. The primary header contains information about the object and the observation and the primary data unit is empty. The spectrum itself is a binary table located in the first extension with three columns: lambda (wavelength in Å in the reference system of the target), flux (rectified flux possibly corrected for resolution effects to ensure uniformity across the survey), and fluxorig (rectified flux without correction). In IDL (with the IDL Astronomy User's Library in the path) the header information can be retrieved with e.g. hdr = HEADFITS('name.fits') and the data themselves with v = MRDFITS('name.fits',1). Then, do e.g. HPRINT, hdr and PLOT, v.lambda, v.flux. Tables in IRAF can be read with TABLES.


Link to load the GOSSS spectrum in VOSpec. You need Java, it is slow, and is not very convenient... but that tool is what I have found. If you know of another tool that can be used as a link and where you can upload a FITS table (or similar), please let me know and I will consider it.

RA: Right ascension in HH:MM:SS.sss (J2000).
dec: Declination in (J2000).

(2) HD/HDE numbers + components


Henry Draper main catalog/extension ID.

Component identification for multiple systems. Suppose we have a system "Star" with two components A and B. There are three possible cases: [1] If A and B have a separation large enough (for their magnitude difference) to have individually extracted spectra, then the two components are called "Star A" and "Star B". [2] If the separation is not sufficient to obtain individual spectra and the magnitude difference is 2.0 or smaller (the threshold we use to determine that the secondary influences the combined spectrum), then the GOSC entry is called "Star AB" and GOSC maintains an internal (non-public) entry for the secondary component as "Star B". [3] If the separation is not sufficient to obtain individual spectra and the magnitude difference is larger than 2.0, then the GOSC entry is called "Star" and GOSC maintains an internal (non-public) entry for the secondary component as "Star B". Note that a priori it is not always straightforward to know whether we will be able to separate the components or not, so the initial name for the main component may change over time. Indeed, it is possible for a system to remain unresolved after one or several observations and then to be resolved when a spectrum with excellent seeing is obtained.

(3) Approximate BJ photometry


Approximate B photometry (Tycho-2 or Johnson) rounded to a tenth of a magnitude.
Jap: Approximate J photometry (2MASS) rounded to a tenth of a magnitude.
Bap-Jap: Approximate B-J color rounded to a tenth of a magnitude.
Fpr: Proximity flag for the photometry. This flag is used when known visual components are likely to affect the e.g. Tycho-2 or 2MASS photometry. In those cases, additional sources such as the WDS or AstraLux imaging have been used to correct the photometry so that it corresponds to that of the brightest visual component.

(4) Extended identifications

Tyc: Tycho-2 catalog number. The link points to the VizieR selection page with Hipparcos- and Tycho-related catalogs.
2MASS: 2MASS catalog number. The link points to the VizieR selection page with the 2MASS catalog.
WDS: Washington Double Star catalog number and link to VizieR.
other: Other name(s) used for the star.
Simbad: Simbad name.

(5) GOSSS spectral classifications

STv3: Spectral type
LCv3: Luminosity classification
qualv3: Qualifier.
secv3: Existence of secondary component(s) in the unresolved spectrum.
refv3: Reference. The link points towards the corresponding ADS web page.

(6) Alternate spectral classifications

Alternate modern spectral types that use high (spatial or spectral) resolution spectroscopy to identify multiple components.

STal: Spectral type
LCal: Luminosity classification
qualal: Qualifier.
secal: Existence of secondary component(s) in the unresolved spectrum.
refal: Reference. The link points towards the corresponding ADS web page.

(6) Previous spectral classifications

Pre-GOSSS spectral classifications

STo: Spectral type
LCo: Luminosity classification
qualo: Qualifier.
seco: Existence of secondary component(s) in the unresolved spectrum.
refo: Reference. The link points towards the corresponding ADS web page.

(7) Additional coordinate information

RA: Right ascension in degrees (J2000).
dec: Declination in degrees (J2000).
ty: Type flag for the coordinates. Please note that the precision of the values for the coordinates is a function of this flag.
As: Relative astrometry from AstraLux, HST, or WDS data, absolute astrometry from Tycho-2 or 2MASS.
G2: Gaia DR2.
M1: 2MASS.
M2: 2MASS (uncertain).
Ot: Other source.
TA: Main Tycho-2 catalog, columns 5 and 6 (with proper motion).
TB: Main Tycho-2 catalog, columns 28 and 29 (without proper motion).
TC: Tycho-2 supplement 1, precessed to J2000.0 with proper motion.
TD: Tycho-2 supplement 1, precessed to J2000.0 without proper motion.
TE: Tycho-2 supplement 2, precessed to J2000.0 with proper motion.
TF: Tycho-2 supplement 2, precessed to J2000.0 without proper motion.
U1: USNO-B1.0.
l: Galactic longitude in degrees.
b: Galactic latitude in degrees.

(8) Johnson photometry


Johnson U magnitude.


Johnson U uncertainty.


Johnson B magnitude.


Johnson B uncertainty.


Johnson V magnitude.


Johnson V uncertainty.
PS: Photometric sets used in Maíz Apellániz & Barbá (2018): J2G, J2GT, J2GS, or J2GTS. An additional i indicates a problem with at least one of the 2MASS bands (missing, saturation, or IR excess). An additional g indicates that the Gaia DR1 G magnitude is missing or was not used.

(9) Clusters/Associations

clusters/nebulae: Young cluster/nebula membership from the WEBDA, Dias et al., NGC 2000, Sharpless (1959), RCW (1960) , and WISE lists (plus modifications). Blue is used for manual entries and black for automatic ones.
associations: Association membership from the Humphreys (1978) and de Zeeuw et al. (1999) lists (plus modifications). Blue is used for manual entries and black for automatic ones.



v 0.0:

November 2002. First version with 379 stars.
v 0.1: December 2002. Typos in the spectral types for HD 152 386, HD 156 212, and HD 216 532 were corrected. Also, a double entry for HD 93 632 was eliminated (it also appeared as "HD 9332"), reducing the total number to 378 stars.
v 0.2: February 2003. A misidentification for HD 95 589 (it appeared as HD 95 549) was found and corrected.
v 0.3: July 2003. A double entry for HD 97 950 was eliminated and HD 93 249 was introduced after having been left out by a software error. Proofreading revealed errors in the spectral types of CPD -28 2561 and HD 37 022 and in the qualifiers of Herschel 36, HD 39 680, HD 46 223, HD 37 041, HD 91 651, HD 94 024, CPD -59 2635, and HD 152 219.
v 1.0: October 2003. First major additions to the catalog after v 0.0. Inclusion of Hipparcos parallaxes and distances, ground-based optical and 2MASS NIR photometry, multiplicity, and group membership information. Also, nomenclature was changed to adjust it to IAU criteria. Erroneous coordinates for three stars in Cyg OB2 (4, 5, and 11) were corrected. Spectral types for WR companions in the supplement were added.
v 1.1: February 2005. The corrected 2MASS magnitudes (with the zero-point offsets of Cohen et al. 2003) were replaced by the original 2MASS magnitudes (no offset applied) in order to make GOSC compatible with CHORIZOS (Maíz Apellániz 2004). An error in the U-B color of HD 11 852 was corrected. The spectral type of HD 228 766 was updated. The nomenclature of a few stars was changed.
v 2.0: December 2006. Overhaul of the catalog: [a] creation of supplements 2, 3, and 4; [b] compilation of alternate spectral classes; [c] addition of Cousins RI photometry; [d] revision of photometry flags; and [e] creation of index cards for each star. Tycho-2 photometry for HD 218 195 was corrected. Coordinates for Cyg OB2-22 A and Cyg OB2-22 B were corrected. HD 93 129 A changed to HD 93 129 AaAb.
v 2.1: October 2008. Some typos corrected. CW CMa changed to UW CMa. HD changed to HDE for stars with ID greater than 225 300. HD 161 853 moved from the catalog to supplement 4. Some clasifications updated. Flag 'P' added to photometric discrepancies. Added more O stars found in the literature.
v 2.2: June 2009. Added Cyg OB2 photometry from Massey et al. 1991. Added 2MASS photometry for 11 stars in the main catalog. Duplicated star deleted from the second suplement (G353.17+00.89_4 = G353.17+00.89_2). General coordinates revision (some of them changed from U1-U2 to M1-M2, others obtained from HST images)
v 2.3: August 2010. Major format and code change. Use of MySQL + IDL to make searches possible. Results from Mason et al. (2009) added. New web page design. Several typos corrected, additional name information added, and minor format changes introduced. 
v 2.3.1: December 2010. Several corrections. 
v 2.3.2: February 2011. Multiplicity data updated. Several corrections. 
v 2.3.2: April 2011. Several format changes. Confusion between HD 160 641 and HD 161 853 fixed. 
v 2.4: March 2012. Conversion of the Multiplicity + Membership information into Clusters/Associations. Links to VizieR added for WDS information. Introduction of the possibility to show/hide columns in the output. Minor redesign of web page to accomodate internal changes on coordinate treatment.
v 3.0: June 2013. Overhaul of the catalog to base it on the GOSSS spectra (DR1.0). FITS spectra available for the first time.
v 3.1: December 2013. Revision of GOSSS spectral types (DR1.1). ALS 15 229 removed from catalog. New capabilities of FITS spectra (headers, new rectification, VOSpec, original and corrected fluxes). New search form (addition of FITS table output, sorting by approximate BJ protometry, addition of a third restriction, restrictions by approximate BJ photometry). Update of external data (e.g. literature spectral types).
v 3.1.1: August 2014. Inclusion of WISE H II regions in clusters and nebulae. Uniformization of the type flag for coordinates. Minor revision of three spectral types (ALS 15 204, CPD -41 7721 A, and HD 207 198): GOSSS DR 1.1.1.
v 3.1.2: July 2015. Overall revision of coordinates, Tycho-2 and 2MASS magnitudes, and names. GOS_ID changes for two stars based on a slight coordinate shift. HD 124 314 A (from 312.67-00.43_01 to 312.67-00.42_01) and HD 124 314 BaBb (from 312.67-00.43_02 to 312.67-00.43_01).
v 3.2: February 2016. GOSSS DR2.0. 142 new O stars added, revised spectral types for some existing stars, and reinstatement of supplement 3 with 11 stars.
v 3.2.1: March 2016. Addition of 2MASS catalog numbers.
v 3.2.2: April 2016. Addition of Simbad names.
v 4.0: December 2017. Move of main GOSC site from IAA to CAB: new URL is Addition of Johnson photometry from Maíz Apellániz & Barbá (2018).
v 4.1: June 2018. GOSSS DR2.1. Addition of O and BA stars and spectral classifications from Maíz Apellániz et al. (2018a) and Maíz Apellániz et al. (2018b).
v 4.2: November 2019. GOSSS DR2.2. Addition of GOSSS and alternate spectral classifications from Maíz Apellániz et al. (2017), Maíz Apellániz et al. (2019), and Maíz Apellániz (2019).


Number of stars in each version of GOSC. Note that the meaning of the supplements changed in v3.0.

Version 0.0 0.1 0.2 0.3 1.0 1.1 2.0 2.1 2.2 2.3 2.3.1 2.3.2 2.3.3 2.4 3.0 3.1 3.1.1 3.1.2 3.2 3.2.1 3.2.2 4.0 4.1 4.2
Main Catalog 371 370 370 370 370 370 370 369 369 369 369 369 370 370 449 448 448 448 590 590 590 590 594 611
Supplement 1 8 8 8 8 8 8 8 8 8 8 8 8 8 8 --- --- --- --- --- --- --- --- --- ---
Supplement 2 --- --- --- --- --- --- 781 857 856 857 857 857 856 856 --- --- --- --- --- --- --- --- 24 32
Supplement 3 --- --- --- --- --- --- 21 22 22 22 22 22 22 22 --- --- --- --- 11 11 11 11 11 12
Supplement 4 --- --- --- --- --- --- 28 29 29 29 29 29 29 29 --- --- --- --- --- --- --- --- --- ---
Total 379 378 378 378 378 378 1208 1285 1284 1285 1285 1285 1285 1285 449 448 448 448 601 601 601 601 629 655



The current version of GOSC includes only stars in GOSSS-DR2.2. Future data releases will raise the number of stars in the catalog and supplements to over 2000.



Support for this work was provided by [a] the STScI DDRF (grant 82 280); [b] the STScI summer student program; [c] NASA (HST GO grants 10 205, 10 602, and 10 898); [d] the Spanish Government (grants AYA2007-64 052, AYA2010-17 631, AYA2010-15 081, AYA2013-40 611-P, AYA2016-75 931-C2-2-P, and PGC2018-095 049-B-C22 and the Ramón y Cajal Fellowship program); [e] FEDER funds; and [f] the Junta de Andalucía (grant P08-TIC-4075).

Corrections, additions, suggestions, and broken-links reports are very much welcomed at  jmaiz [at] .